Adaptive differentiation and rapid evolution of a soil bacterium along a climate gradient

Area of Science:

• Microbiology
• Ecology
• Evolutionary Biology

Background:

• Microbial responses to environmental change are often studied through ecological processes.
• The rapid evolution and adaptation potential of microbes in natural settings is under-explored.

Purpose of the Study:

• To investigate how ecological and evolutionary processes concurrently influence soil microbiome genetic diversity.
• To assess microbial community adaptation to climate gradients in Southern California leaf litter.

Main Methods:

• Two concurrent 18-month field experiments using reciprocal transplantation of microbial communities and an isogenic strain of *Curtobacterium*.
• Genomic and metagenomic analyses to track ecotype shifts and identify mutations.
• Studied microbial adaptation across a climate gradient in leaf litter.

Main Results:

• Transplanted microbial ecotypes converged towards native community types on a common substrate.
• Observed shifts correlated with *Curtobacterium* ecotype traits, suggesting local adaptation to climate.
• Identified nonrandom, parallel mutations in genes for nutrient acquisition and stress response in transplanted *Curtobacterium*.

Conclusions:

• Both demographic shifts of adapted ecotypes and contemporary evolution shape soil microbiome diversity on similar timescales.
• Demonstrates the interplay of ecological and evolutionary dynamics in microbial adaptation to environmental change.